The present invention regards a new composite panel and a method of manufacturing waterproof roofings for buildings.
The remaking of an old waterproof roof can be effected either by applying to the existing roofing a non-waterproofing mantle after all proper repairs have been carried out, or by directly applying a new mantle onto the structure of the roof after having entirely eliminated the old covering. Especially when adopting the first solution it is always very difficult to obtain a well levelled new surface, which is thus suitable for receiving a new waterproofing mantle since the old mantle is often badly damaged in that it has cracks and undulations.
To obviate this drawback, resort has been made to a method that comprises the following operations.
1. Dry-laying on the old mantle or cover, panels made of a rather rigid material, having a thickness of about 2.5 cm, i.e. panels on which one can walk, and having the function of supporting a new waterproofing membrane and increasing the insulating capacity of the roofing.
2. Securing the panels to the roof structure through mechanical fastening by means of flush-head nails of suitable type and in appropriate number.
3. Dry-laying of a bituminized feltpaper (e.g. of the 500 g/m type) on the panels, which has the function of protecting the panels against the action of the flame that is used for applying a further layer of waterproofing material. This is done when the panel consists of inflammable material.
4. Application and fixing of feltpaper to the panels.
5. Laying a first waterproofing layer or membrane by causing it to fully adhere to the panels covered by the feltpaper by means of a propane torch.
6. Laying of a top waterproofing layer which completely adheres to the first layer.
Thus, at least six operations are necessary for remaking the waterproofing of a roof or for the application of a new roofing, which involves excessive labour expenses and time.
It should also be stated that panels conventionally used for this purpose are rather brittle, poorly adherent and have a low degree of flexion per unit load.
To reduce the risk of breakings, use is made of panels having reduced dimensions. This requires, however, a large number of fixing nails and points or seams in the roofing.
Moreover, the weaker the structure of the panels, the poorer the grip of the nails. Thus, it is necessary to increase the quantity of nails to ensure proper fixing, but this is uneconomic besides being inconvenient from the structural point of view.